I ended up ordering a DX90 yesterday. I originally was interested in the AK100 but the impedance issue steered me to the X5 and DX90. I remember Jamato8 from his sage advice in the past and decide to take a chance on the Ibasso. I am pairing it with my JH13 and Roxanne iem. My sources up to this point has been recently Cowon S9, Sansa clip +, and BB Z10 using Neutron app. I'm a musician, bass player. I started out this adventure with Archos first mp3 player years ago.....scratch that, when I was about 7 years old and had what was called a "show n tell record player". It had a film strip that would advance as the record played. My parents had a restaurant, and we had a jukebox. I'm not sure how it worked, but after a certain period of time, the owners of the jukebox would replace the records and would give us the old records. Here I was a 7 year old with 100's of 45's for my enjoyment! I still remember the very first 45 I played, it was Paul Mccartney and Wings, side A was Jet and side B was mamunia. It might have been low fidelity, but that sparked an interest in music that lives on to this day.

Give me little more time for sound impression.
USB-DAC seems to be appear on the option menu. To switch from storage mode to dac mode. Need to get back home and try whether it is working or not.
There is a rescan library button which means you dont need to taking the microsd in and out for scanning.
The 3 main button still have some input lag.

Update:
The USB-DAC function is not working due to driver problem. Maybe it's my problem. I've sent a email to ibasso. Hope getting reply soon.
Promise of picture of the dx90. I'm not a photographer.Edited by tin427 - 4/12/14 at 2:16am

I use an amp, the PB2. Can anyone tell me if I'll get huge benefits going from the DX50 to the DX90

Not that many people can help you with the DX90, so far only @jamato8 had the player, starting next week it will be a different story. What I can say because I have the DX50, I currently have a stack I carry around, an amp and the player because I was not happy with the player alone and mostly because of the volume bug. I am hopping the DX90 does not have the bug and that its amp is better. If that is the case, I will be carrying a smaller stack, just the player. This is where you would at least benefit. The other benefit could be the sq, that is to be determined next week. " src="http://files.head-fi.org/images/smilies/wink.gif" />